1. Field of the Invention
The present invention relates to an organic light-emitting diode (OLED) display device, and more particularly, to an OLED display device and a method of fabricating the same, to realize the simplified process.
2. Discussion of the Related Art
Among various display devices which represent information as images, an organic light-emitting display device has attracted great attentions owing to its thin profile corresponding to paper. The organic light-emitting display device using a thin organic light-emitting layer formed between electrodes emits light by itself, which is referred to as an electro-luminescence display device or an organic light-emitting diode display device (hereinafter, which is referred to as an OLED display device). The OLED display device has the advantageous properties of lower power consumption, thinner profile and greater self-light emission as compared to those of a liquid crystal display device. In the meantime, the OLED display device has the disadvantageous properties of short lifespan.
The OLED display device is developing in an active matrix type which is suitable for displaying moving images by separately driving sub-pixels of red, green and blue colors included in one unit pixel. The active matrix OLED (AMOLED) display device includes a plurality of sub-pixels, wherein each of the sub-pixels is comprised of an organic light-emitting diode (OLED) including the cathode, the anode and an organic light-emitting layer formed between the cathode and the anode; and a sub-pixel driver to drive the OLED independently. Each sub-pixel driver includes at least two thin film transistors and a storage capacitor, wherein the sub-pixel driver controls the brightness of OLED based on a current amount supplied to the OLED. Also, the OLED includes a hole-injection layer, a hole-transport layer, a light-emitting layer, an electron-transport layer, and an electron-injection layer provided between the cathode and the anode and formed of an organic material. As a forward-directional voltage is applied between the cathode and the anode, electrons of the cathode are moved to the light-emitting layer through the electron-injection layer and the electron-transport layer. Also, holes of the anode are moved to the light-emitting layer through the hole-injection layer and the hole-transport layer. The light-emitting layer emits the light by recombination of the electrons supplied through the electron-transport layer and the holes supplied through the hole-transport layer. At this time, the brightness of emitted light is proportion to the current amount flowing between the cathode and the anode.
The related art AMOLED display device is formed in an encapsulation structure where a substrate including both a sub-pixel driving array and an OLED array is bonded to a packaging plate, wherein the light is emitted through the substrate including the sub-pixel driving array and the OLED array. The packaging plate includes a getter material which absorbs moisture and gas, to thereby prevent the organic light-emitting layer from being deteriorated. If defects occur in the process of OLED array after completing the process of sub-pixel driving array, the substrate is disused whereby the yield is lowered. Also, it is difficult to apply the packaging plate to a high-resolution display device since the packaging plate limits an aperture ratio.
In order to overcome these problems, there is a recent development for a dual-plate type AMOLED display device where sub-pixel driving array and OLED array are formed on different substrates. However, the dual-plate type AMOLED display device has the disadvantageous properties in that a lower substrate including the sub-pixel driving array requires more mask processes as compared with an upper substrate. Accordingly, there is a need to decrease the number of mask processes for the lower substrate, thereby lowering the fabrication cost.